Elon Musk will get paid for building the world’s largest lithium ion battery in South Australia, with testing on the 100-megawatt project about to begin ahead of next week’s December 1 deadline to build it in 100 days, or it’s free.

State premier Jay Weatherill announced today that regulatory testing at the site, which is paired with French energy business Neoen’s Hornsdale wind farm, 230 kilometres (143 miles) north of the capital, Adelaide, will begin within days.

When fully charged, the Tesla Powerpack is expected to hold enough power for 8,000 homes for 24 hours, or more than 30,000 houses for an hour during a blackout.

The project is part of an AU$550 million plan by the state to guarantee energy supply following a statewide blackout last year that turned into a national political debate over energy security and costs.

A 250MW gas-fired generator, expected to cost AU$360 million, is also due to come online this summer to provide extra power.